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England has achieved relatively high vaccine coverage with at least one dose of vaccine having been given to three out of four citizens, for age groups 18 years and above. This is good news for the country, which has been hard-hit by the coronavirus disease 2019 (COVID-19) since March 2020.

A new study reports this finding, along with varying antibody prevalence among different groups and regions and between different age groups. In the current paper, available as a preprint on the medRxiv* server, the results of the sixth round of the REACT-2 study are reported.

In the earlier rounds, significantly varying rates of COVID-19 prevalence by region, ethnic origin and occupation were reported. In succeeding rounds, the seroprevalence dropped gradually, as antibody levels declined, but then rose again, as a result of the second wave of viral spread as well as an increase in vaccine coverage.

The current round was carried out from May 12 to 25, 2021, covering over 207,000 adults who self-tested using the LFA. This number comprises less than a third of those invited, but over 80% of all who registered for the test.

Background

The REACT-2 (REal-time Assessment of Community Transmission-2) is a cross-sectional random community survey of adults in England, has been going on in England ever since the early days of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

The methods include questionnaires to elicit symptomatic infections coupled with lateral flow immunoassay (LFA) testing to detect evidence of past or current infection. The detection of immunoglobulin G (IgG) antibody to the SARS-CoV-2 spike protein was used as a proxy for the prevalence of infection before the vaccination program began.

The COVID-19 vaccine rollout in England began in December, 2020, in a phased manner, prioritizing those at the highest risk of infection and of severe symptomatic disease. Rapid implementation of the vaccination program occurred, assisted by introducing a practice of delayed second doses to 12 weeks after the first. By the beginning of July 2021, 85% of adults in England had received one dose, and almost two in three had received both doses.

Evidence is accruing that rapid vaccine coverage has helped bring down SARS-CoV-2 transmission, reduce hospital admissions and the death rate from COVID-19.

Vaccine coverage

The researchers found that of the study sample, approximately 73% of adults were vaccinated with at least one dose. However, this included only one in four of those aged 18-24 years, but almost all those aged 75 or more.

Health workers were approximately ten times more likely to be vaccinated, and care workers four times, relative to non-essential workers, while those in the field of education had 63% increased odds relative to other fields of work. Unfortunately, workers in the areas of hospitality and retail, who would be expected to have contact with the public, had approximately 30% lower odds of vaccine coverage compared to other workers.

Even so, men were 10% less likely to have been vaccinated than women, while Black people had 60% lower odds of having received the vaccine. Conversely, Asian people had 13% higher odds.

Socioeconomic deprivation was also inversely linked to vaccine coverage, and those who reported having had COVID-19 already were 40% less likely to be vaccinated. Londoners had 14% lower odds, while those in the Northwest of England had 23% higher odds of being vaccinated relative to Southeast England.  

What about vaccine hesitancy?

The scientists found that about 98% of participants said they had been or intended to be vaccinated when they became eligible. The percentage of vaccine hesitancy or unwillingness declined across age groups, with less than 1% of people identifying themselves as such.

The most unwilling were those aged 25-34 years, with 25% more hesitancy than those aged 35-44 years. Poorer and less educated people also showed slightly more hesitancy, as did those of Black or mixed ethnic origin, compared to Caucasian or Asian origin.

A history of COVID-19 or smoking also pushed up the risk of hesitancy. Overall, the reasons most often given for hesitancy were fear about the long-term adverse effects or wanting to have evidence of vaccine efficacy. However, this reason was less often proffered in this round compared to earlier rounds.

What was antibody prevalence?

The results showed that antibody prevalence went up remarkably following the implementation of vaccination. The increase to 61% contrasts with 14% and <7% in the previous two rounds. The lowest prevalence was in the Northwest, at 58%, vs. 62% among Londoners.

Taking individual local authorities, the variation was greater, from 40% to 79%. Health workers were eight times as likely to be seropositive than other or non-essential workers, while care workers had four times higher odds. Essential workers had 30% increased odds compared to other non-essential workers.

Again, age predicted higher seroprevalence, with 95% of those aged 75 or more showing anti-spike antibodies vs. 36% of those aged 18-24 years. This trend, mirroring vaccine coverage, persisted with respect to ethnicity, with Asians showing 67%, Blacks 55%, but mixed 17%, and other races 37% higher odds of seropositivity.

Men were at 30% lower odds to be seropositive, however, but deprivation did not show a significant effect in this area. Hospitality and retail workers had 30% to 40% lower odds of antibody positivity.

Post-vaccine antibody positivity

Antibody positivity rose after the first and second doses, with a decline at 4-5 weeks after the first dose, lasting up to 11 weeks. Positivity was higher in those with a history of prior infection, and the Pfizer vaccine recipients also had higher odds of seropositivity relative to the Astra-Zeneca vaccine.

After two doses, the Pfizer vaccine was associated with 100% seropositivity at all ages except at 80 years and above, this group showing 98% positivity. With the AstraZeneca vaccine, approximately 90% or more of those up to 79 years were seropositive, vs. 84% of those older than this.

Single-dose positivity ranged from 100% in the 18-29 years to 32% in those aged 70-79 years for the Pfizer vaccine. In contrast, the Astra-Zeneca vaccine produced 72% seropositivity in the youngest, but only 46% in the 80 years and over the group. A few received the Moderna vaccine with high seropositivity rates.

What are the implications?

The study shows that vaccination has been implemented in a rapid and large-scale fashion in England among adults, producing a relatively higher antibody prevalence after two vaccine doses. The lowest coverage is in the youngest eligible group, who have the lowest vaccine priority, as well as in some disadvantaged groups, among men and London dwellers.

Among workers facing the public, both vaccine coverage and seroprevalence were low, indicating they remain at higher risk of infection and hence may transmit the infection. Those with a history of COVID-19 had lower coverage, perhaps because a four-week delay is recommended in this group or because such individuals feel they are already immune.

A satisfying rise in antibody prevalence is observed after 70% coverage with at least one dose of a COVID-19 vaccine. The rise is clearest after the second dose, which implies that both doses must be taken when offered. The dramatic rise after the second dose, especially since antibody titers fall between weeks 4-11 after the first dose, bears out the need to reduce the period between the first and second doses during a period of rapid spread.

Further research is required to elicit the link between being positive for IgG against the virus, and neutralizing capacity, which alone can hinder infection and transmission. It is also possible that emerging variants such as the delta strain will not be neutralized unless high protective antibody titers are achieved.

Deprivation is linked to poorer vaccine coverage, whereas non-White ethnicity was associated with higher seropositivity due to a greater risk of infection. Overall, encouraging vaccination rates and seropositivity prevalence is set off by lower coverage and antibody prevalence in some groups.

Obtaining improved rates of vaccination in these groups is essential to achieving high levels of protection against the virus through population immunity,” the authors point out.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.